You can use the location tab on the desktop folder(or any users folders like documents/download/pictures/ect) in Windows 8.1 to set the desktop location to the hard drive. The tab is under the folder properties at c : \ users \ yourname here
Example Image. While this is 7, it is the same for 8/8.1
As for games, steam can make a library for games on the hard drive.
Programs and many non steam games should be installed fresh since they make registry entries that will not be on the new load of Windows 8. Most programs/games allow you to select an install location(sometimes under advanced install or custom install.).
as an example you would have
c : with windows
d : / your name / documents
d : / your name / desktop
d : / your name / downloads
d : / your name / ect
d : / Games / steam
d : / Programs /
Then you can set things up the way you want them.